Process for producing L-threonine

Abstract

L-threonine is produced by aerobically culturing a bacterium belonging to the genus Acinetobacter, which utilizes ethanol and has an ability to produce and accumulate L-threonine, in a culture medium in which ethanol is the main carbon source to produce and accumulate L-threonine in a culture liquor and recovering L-threonine from the culture liquor. The bacterium is preferably a mutant of Acinetobacter calcoaceticus YK-1011 (Ferm-P No. 5910).

What is claimed is: 
     
       1. A process for producing L-threonine from a mutant bacterium which utilizes ethanol and has the ability to produce and accumulate L-threonine when culturing said bacterium, comprising aerobically culturing a mutant bacterium obtained by mutagenizing Acenetobacter calcoaceticus YK-1011 having FERM-P No. 5910, in a culture medium in which ethanol is the main carbon source to produce and accumulate L-threonine in a culture liquor and then recovering L-threonine. 
     
     
       2. The process of claim 1, wherein said mutant bacterium is Acinetobacter calcoaceticus YK-1014 having FERM-P No. 4818. 
     
     
       3. The process of claim 1, wherein said mutant bacterium is obtained by mutagenizing with N-methyl-N'-nitro-N-nitrosoguanidine. 
     
     
       4. The process of claim 1, wherein said mutant bacterium is cultured at a temperature of 20° to 40° C. and a pH of 4-10. 
     
     
       5. The process of claim 1, wherein said mutant bacterium is cultured at a temperature of 25° to 38° C. and a pH of 6-8. 
     
     
       6. The process of claim 1, wherein L-threonine is recovered using an ion exchange resin, activated carbon, or concentration-crystallization. 
     
     
       7. The process of claim 1, wherein an initial concentration of said ethanol is 1-5% volume/volume.